1. Field
The present invention relates to pyroelectric materials, pyroelectric sensing devices which detect the temperature of objects from their radiations and pyroelectric imaging devices which portray objects by temperature differences between parts of the object and/or its surroundings.
2. Prior Art
The use of pyroelectric materials for infrared (IR) detection and thermal imaging is now a well established technology. This technology offers some distinct advantages over the rival technology of IR photoconductive detectors. Pyroelectric detectors require no refrigeration, therefore, imaging systems that use them are much less expensive and more portable. Such imaging systems, however, do not as yet match the brightness and definition provided by cooled photodiodes. To bridge this performance gap there is a need for pyroelectric detectors or sensors with much higher sensitivity and spatial resolution. The performance of materials used in integrated circuit pyroelectric arrays, thermistor type holometric arrays and vidicon TV cameras are generally compared by means of a Figure of Merit which takes into account the effects of frequency, noise and similar parameters on the systems performance. To have a high Figure of Merit (or good performance) pyroelectric materials must have a Curie temperature (T.sub.c) near room temperature. To make thin inexpensive high definition arrays, suitable for use with silicon charge-coupled-devices (CCD's), it would be advantageous to make use of the more rugged ceramic type materials such as lead titanate which have high spontaneous polarization (75 Coul./cm.sup.2), but which unfortunately normally have Curie temperatures near 500.degree.C.